A METHOD FOR CALCULATION OF FREE-SPACE SOUND PRESSURES NEAR A PROPELLER IN FLIGHT INCLUDING CONSIDERATIONS OF THE CHORD WISE BLADE LOADING

摘要

The general expressions of NACA Report 1198 for determining the sound-pressure field for a rotating propeller in uniform subsonic flight are reviewed for the case of a propeller with uniform chordwise forces. Consideration is given to effects of nonuniform chordwise and radial blade loading. Tabulated values of certain definite integrals that are involved in the calculation of a near-field propeller noise regardless of the form of the chordwise forces are presented. These tabulations cover a wide range of operating conditions and are useful for estimating propeller noise when either the concept of an effective radius or radial distributions of forces are considered. In order to illustrate their use, the tabulations are used in conjunction with the concept of an effective radius to make evaluations for some specific propellers. Results of these evaluations are presented and discussed.